Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$210.43	6.139%	$223.3483	$223.35	$223.35	$223.30
Purchase #2	$191.67	7.676%	$206.3826	$206.38	$206.40	$206.40
Purchase #3	$168.96	7.808%	$182.1524	$182.15	$182.15	$182.20
Purchase #4	$92.84	9.233%	$101.4119	$101.41	$101.40	$101.40
Purchase #5	$189.89	3.630%	$196.783	$196.78	$196.80	$196.80
Purchase #6	$152.73	10.526%	$168.8064	$168.81	$168.80	$168.80
Purchase #7	$11.36	11.818%	$12.7025	$12.70	$12.70	$12.70
7 purchase totals =	$1,017.88		$1,091.5871	$1,091.58	$1,091.60	$1,091.60